MAX3233E Maxim, MAX3233E Datasheet - Page 10

• Manufacturer Part Number: MAX3233E
• Description: 15kV ESD-Protected / 1A / 250kbps / 3.3V/5V / Dual RS-232 Transceivers with Internal Capacitors
• Manufacturer: Maxim

±15kV ESD-Protected, 1µA, 250kbps, 3.3V/5V, Dual
RS-232 Transceivers with Internal Capacitors
Figure 7. Transmitter Outputs when Exiting Shutdown or
Powering Up
that measured using the Human Body Model. Figure 6a
shows the IEC 1000-4-2 model, and Figure 6b shows the
current waveform for the ±8kV, IEC 1000-4-2, Level 4,
ESD contact-discharge test.
The air-gap test involves approaching the device with a
charged probe. The contact-discharge method connects
the probe to the device before the probe is energized.
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to emulate the stress caused by
contact that occurs with handling and assembly during
10
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
10V/div
t r = 0.7ns to 1ns
5V/div
2V/div
______________________________________________________________________________________
0
0
0
100%
V
90%
10%
FORCEON = FORCEOFF
CC
I
= 3.3V
30ns
10 s/div
60ns
Machine Model
T1OUT
T2OUT
t
manufacturing. Of course, all pins require this protec-
tion during manufacturing, not just RS-232 inputs and
outputs. Therefore, after PC board assembly, the
Machine Model is less relevant to I/O ports.
The MAX3233E/MAX3235E do not require external
capacitors to operate their internal charge pumps.
The MAX3235E can be operated down to 3.0V by par-
alleling the internal C1 capacitor with an external 0.1µF.
When using an external capacitor across the C1 termi-
nals, check to confirm that the total supply voltage
measured from V+ to V- does not exceed the absolute
maximum voltage of 13V. With the external 0.1µF
capacitor added, the MAX3235E should not be used
with a supply greater than +3.9V.
In most applications, a 0.1µF V
adequate. Connect bypass capacitors as close to the
IC as possible.
Figure 7 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two trans-
mitter outputs are shown going to opposite RS-232
levels (one transmitter input is high, the other is low).
Figure 8. Loopback Test Circuit
__________Applications Information
V
V
CC
CC
C
BYPASS
FORCEOFF
T_ IN
R_ OUT
FORCEON
MAX3233E
MAX3235E
Power-Supply Decoupling
GND
when Exiting Shutdown
V
CC
Transmitter Outputs
CC
T_ OUT
5k
R_ IN
bypass capacitor is
Charge Pumps
1000pF